When a colony of honey bees grows to about 4,000 members, it triggers an important first stage in its reproductive cycle — the building of a special type of comb used for rearing male reproductives, also known as drones. Drones are male honey bees that develop from unfertilized eggs. Their sole purpose in a colony is to mate with virgin queens from other colonies, thereby spreading the genes of the colony that produced the successful drones.

A team of experts from the Department of Neurobiology and Behavior at Cornell University, led by Michael Smith, studied what starts the reproductive cycle of honey bee colonies. The results are published in the journal Naturwissenschaften.

They found that while every colony built worker comb (non-reproductive comb), not every colony built drone comb (reproductive comb). In fact, only an increase in the number of workers stimulated the workers to start constructing drone comb. This was seen whenever colonies contained 4,000 or more worker bees.

“Colonies with more workers built a greater proportion of drone comb, but colonies with more comb, more brood, or more honey stores, did not do so,” Smith summarizes. “We estimate that a colony needs approximately 4,000 workers to invest in building drone comb.”

The researchers were still left wondering about precisely how an individual worker bee knows how many other workers there are in its colony. Smith and his team speculate that this might have to do with how crowded individuals feel while working side by side in the hive. They are currently engaged in further research to shed more light on this mystery.

The researchers believe that their findings are also relevant to other social systems in which a group’s members must adjust their behavior in relationship to the group’s size.